CZ164198A3 - Bituminous mixtures and process for preparing thereof - Google Patents

Abstract

The invention provides a process for preparing a bitumen composition comprising blowing a mixture with an oxygen-containing gas which mixture comprises a bitumen having a penetration of less than 300 dmm (as measured by ASTM D 5 at 25 DEG C) and a thermoplastic rubber which is present in an amount of less than 5 wt.%, based on total mixture; bitumen compositions obtainable by such process; and the use of such bitumen compositions in asphalt mixtures for road applications.

Description

Bituminous mixtures and process for their preparation

Technical field

The present invention relates to bituminous compositions, a process for their preparation and use in asphalt compositions for road applications.

BACKGROUND OF THE INVENTION

The bitumen is used as a binder in road asphalt mixtures and has been continually developed to meet the ever-increasing demands of road construction. In general, bitumen works very well in road asphalt, but the increasing volume of heavy freight traffic leads to premature wear on many roads, resulting in ruts or cracks in the road surface. The cracks represent serious damage to the asphalt road, since water can then reach the lower layers of the road surface, causing rapid deterioration and accelerating the need for premature repairs. Increasing the bitumen content of the asphalt or using a softer grade of bitumen improves the asphalt resistance to cracks at lower temperatures but, on the other hand, increases the risk of excessive rutting at higher temperatures because the mixture is in fact softer. On the other hand, resistance to deformation by excessive loads (ruts) can be increased by reducing the bitumen content of the asphalt mixture or by using a harder bitumen grade, at the expense of crack resistance, since the mixture is less flexible.

In view of the above problems, it is clear that it would be highly advantageous to develop a hard bituminous composition that would meet the current requirements for resistance to cracking, i.e. a bituminous composition having both good low temperature performance and good ejection resistance. track at high temperatures.

It is known that the low temperature behavior of resins can be improved by mixing them with the polymer. However, using this modification in hard resins, generally incompatibility between the resin and the polymer is found, resulting in little or almost no improvement in low temperature behavior and relatively rapid aging.

It is further known from WO gu / 16019 to prepare industrial and roofing bituminous coverings by subjecting the bitumen / polymer mixture to a conventional air blowing process. However, these bituminous compositions do not appear to be suitable for road applications due to their high softening point and relatively high penetration.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a bituminous composition suitable for road applications, which will have both good low temperature behavior and good resistance to rutting at high temperatures, and will also age more slowly.

Surprisingly, it has now been found that such a bituminous composition can be prepared by exposing a certain bituminous composition to the blowing process.

Accordingly, the present invention relates to a method of preparing a bituminous composition which comprises blowing the composition with an oxygen-containing gas, the composition comprising a bitumen having a penetration of less than 300 dmm (measured by ASTM D 5 at 25 ° C) and a thermoplastic rubber which is present in an amount of less than 5% by weight of the total mixture.

Suitably, the thermoplastic rubber is present in an amount of less than 3% by weight, preferably in the range of 1 to 3% by weight of the total composition.

The resin used in this process has a penetration of less than 300 dmm (measured by ASTM D 5 at 25 ° C).

Preferably, the resin has a penetration of less than 250 dmm, preferably less than 200 dmm (as measured by ASTM D 5 at 25 ° C).

Blowing is performed with an oxygen-containing gas such as air or pure oxygen. The best is air.

Suitably, the process is carried out at a temperature in the range of from 200 to 280 ° C.

Preferably, the process of the invention is carried out at a temperature in the range of from 210 to 260 ° C, most preferably in the range of from 230 to 250 ° C.

The process of the invention may be carried out at ambient air pressure or at elevated pressure. Normally, however, it will proceed under ambient air pressure conditions.

The composition comprises a thermoplastic rubber. The composition may comprise one or more different types of thermoplastic rubber. However, it is preferred to use only one type of thermoplastic rubber.

Although a wide variety of thermoplastic rubbers may be used in accordance with the present invention, they contain. preferred thermoplastic rubbers optionally hydrogenated block copolymers consisting of at least two terminal poly (monovinylaromatic hydrocarbon) blocks and at least one central poly (conjugated diene) block.

Preferably, the block copolymer components are selected from the group consisting of those having the formula A (BA) _m or (AB) _n X, wherein A is a predominantly poly (monovinylaromatic hydrocarbon) block, wherein B is a predominantly poly (conjugated diene) block, wherein X represents a residue of a polyvalent coupling agent and wherein n represents an integer> 1, preferably> 2 and m represents an integer> 1, preferably m is 1.

More preferably, blocks A are predominantly poly (styrene) blocks and blocks B are predominantly poly (butadiene) or poly (isoprene). The polyvalent coupling agents to be used include those commonly known in the art.

The term "predominantly" means that both blocks A and B may be mainly derived from a monovinyl aromatic hydrocarbon monomer and a conjugated diene monomer, and these monomers may be mixed with other structurally linked or unlinked comonomers, eg a monovinyl aromatic hydrocarbon monomer as a major component and a small amount (up to 10%) of other monomers or butadiene mixed with isoprene or a small amount of styrene.

More preferably, the copolymers comprise pure poly (styrene), pure poly (isoprene) or pure poly (butadiene) blocks, of which the poly (isoprene) or poly (butadiene) blocks can be selectively hydrogenated to a maximum unsaturation of residual ethylene of 20%. % and preferably less than 5%. Preferably, the block copolymer used has an ABA structure wherein A has an actual molecular weight of 3,000 to 100,000, preferably 5,000 to 40,000 and B has an actual molecular weight of 10,000 to 250,000, preferably in the range of The originally prepared poly (conjugated diene) blocks typically contain from 5 to 50 mol% vinyl groups resulting from the 1.2 polymerization related to conjugated diene molecules, a vinyl content of from 10 to 25% being preferred.

The complete block polymer to be used according to the present invention typically contains polymerized vinyl aromatic monomers in an amount of from about 10 to 60% by weight, preferably from 15 to 45% by weight.

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The actual molecular weight of the total block copolymer will normally be in the range of 15,000 to 350,000, preferably in the range of 40,000 to 250,000.

Examples of suitable pure block copolymers include KRATON G-1651, KRATON G-1654, KRATON G-1657,

KRATON G-1650, KRATON G-1701

KRATON D-1102, KRATON D-1107

KRATON D-1115, KRATON D-1115, KRATON D-1115,

KRATON D-1122, KRATON D-1135X, KRATON D-1184, KRATON D-1144X, KRATON D-1300X, KRATON D-4141 and KRATON D-4158 (KRATON is a trademark).

The bitumen may be a petroleum distillation residue, a cracked residue, a residue obtained by blowing oil or residues from the distillation of crude oil or oil extracts, a resin derived from propane resin, butane resin, pentane resin or mixtures thereof. Other suitable resins include mixtures of the above resins with fillers (plasticizers), such as petroleum extracts, e.g. aromatic extracts, distillates or residues.

Suitably, the resin used has a softening point in the range of 35 to 65 ° C, preferably in the range of 42 to 58 ° C (as measured by ASTM D 36).

One highly surprising and advantageous aspect of this process is that very attractive bituminous compositions can now be prepared under mild conditions without the need for the presence of a bitumen blowing catalyst. Thus, the process of the present invention can take place in the absence of a resin blowing catalyst.

The aforementioned thermoplastic rubbers are preferably unvulcanized thermoplastic rubbers. The use of the unvulcanized thermoplastic rubbers of the present invention has the advantage that the attractive bituminous compositions can be prepared without the need for.

The presence of a vulcanizing agent. Therefore, this process may conveniently be carried out in the absence of a curing agent.

As is known to those skilled in the art, the resin / thermoplastic rubber mixture is heated prior to blowing. The resin / thermoplastic rubber mixture is normally preheated in such a way as to achieve an initial mixture temperature in the range of from 160 to 220 ° C.

The present invention further provides bituminous compositions obtainable by any of the methods described herein. These bituminous compositions correspondingly have a penetration of less than 100 dmm, preferably less than 75 dmm (measured by ASTM D 5 at 25 ° C), and a softening point in the range of 60 to 90 ° C, preferably in the range of 65 to 75 ° C (as measured by ASTM D 36) and contain less than 5% by weight, preferably less than 3% by weight, preferably 1 to 3% by weight of any of the aforementioned thermoplastic rubbers per total bitumen composition. This bituminous mixture is very attractive because it has both very good low temperature performance and very good resistance to rutting.

Fillers such as carbon black, quartz and limestone, stabilizers, antioxidants, pigments and solvents are known to be useful in bituminous compositions and can be added to the compositions of the invention at concentrations known in the art.

The present invention further relates to the use of a bituminous composition as described above in an asphalt composition for road applications.

The invention will now be demonstrated by the following examples.

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DETAILED DESCRIPTION OF THE INVENTION

Example 1

The blend was prepared on a resin basis with a penetration of 100 dmm (measured by ASTM D 5 at 25 ° C), which is an industrially produced non-naphthenic resin, which is prepared by distillation of crude oil. The resin has a penetration index of 0.5 and a softening point at 44 ° C (as measured by ASTM D 36). To this resin was added 2% by weight of block polymer depending on the weight of the total mixture. The block copolymer used was a hydrogenated polystyrene-polybutadiene-polystyrene block copolymer with a 30% by weight styrene content and an average molecular weight of 103,000 as measured by GPC on a polystyrene standard. The ethylene unsaturation of the polymer was reduced by hydrogenation to less than 1% of the initial unsaturation.

The mixture was prepared by mixing the resin and the block copolymer at 180 ° C. Subsequently, the pre-heated mixture thus obtained was blown (air blown) in a blowing vessel at 220 ° C for 2 hours. The basic properties of the blown bituminous mixture are given in Table 1.

Example 2

The comparative blowing process was carried out in a similar manner to that described in Example 1, except that no thermoplastic rubber was added to the resin. The basic properties of the blown resin are shown in Table 1.

The obtained bituminous mixture was subjected to an Oven Rolling Thin Film Test (ASTM D 2572 Test Method). The basic properties of the bituminous mixture after this test are given in the lower part of Table 1.

Example 3

The comparative blowing process was similar to that described in Example 1, except that the block copolymer was added to the resin after it was blown. The basic properties of the blown bituminous mixture are given in Table 1.

Example 4

The process proceeded similarly to Example 1, except that I weight% of the copolymer was added to the resin, depending on the weight of the entire mixture. The basic properties of the blown bituminous mixture are given in Table 1.

The basic properties of the bituminous mixture after undergoing the RTFOT aging test are given in the lower part of Table 1.

From the results presented in Table 1, it will be clear that the process of the present invention (Examples 1 and 4) can produce a hard bituminous composition with attractive low temperature elasticity, as shown by the Fraass strength limit (measured by IP 80), while using processes that not falling within the scope of the invention (Examples 2 and 3) less attractive hard bituminous products are obtained. In addition, as will be clear from Examples 2 and 4, this bitumen composition is more stable in terms of thermal oxidation.

Table 1

Example 1 2 3 4 Mixture Thermoplastic rubber (% by weight) 2 0 2 1 Blowing properties after 2 hours at 220 ° C penetration at 25 ° C (0.1 mm) 24 20 May 16 25 softening point ball method (° C) 67.5 65 81 63 penetration index (-) 0.7 0.0 1.9 0.1 ultimate strength according to Fraass (° C) -13 -5 -2 -10 Properties after aging test (RTFOT) Penetration at 25 ° C (0.1 mm) Retention Penetration (%) Softening Point Ball Method (° C) Softening Point Increase (° C) Penetration Index (-) Fraass Strength Limit (° C) 16 80 72 7 0.7 -3 21 84 65.5 2.5 0.2 -7

Claims (9)

PATENT CLAIMS A process for preparing a bituminous composition which comprises blowing the composition with an oxygen-containing gas, the composition comprising a bitumen having a penetration of less than 300 dmm (measured by ASTM D 5 at 25 ° C) and a thermoplastic rubber present in an amount less than is 5% by weight depending on the total weight of the mixture. The method of claim 1, wherein the thermoplastic rubber is present in an amount of less than 3% by weight depending on the total weight of the composition. Method according to claim 1 or 2, wherein the mixture is blown with air. A method according to any one of claims 1 to 3, wherein the temperature ranges from 210 to 260 ° C. The method of any one of claims 1-4, wherein the thermoplastic rubber comprises an optionally hydrogenated block copolymer which comprises at least two terminal poly (monovinylaromatic hydrocarbon) blocks and at least one center (conjugated diene) block. The method of claim 5, wherein the block copolymer has the formulas A (BA) _m or (AB) _n X, wherein A represents a predominantly poly (monovinylaromatic hydrocarbon) block and wherein B represents a predominantly poly (conjugated diene) block, wherein X represents the remainder of the polyvalent bonding agent and wherein n is an integer> 1 and m is an integer> 1. The method of claim 6, wherein the A blocks are predominantly poly (styrene) blocks and the B blocks are predominantly poly (butadiene) or poly (isoprene) blocks. A bituminous composition obtained by a process as defined in any one of claims 1-7. Use of a bituminous mixture as defined in claim 8 in an asphalt mixture for road applications.